Canine Distemper (Distemper: Out of order, Dysfunctional)
Synonymous
Hard pad disease, Canine plague. The virus was first isolated in the USA in 1905
Etiology:
CD Virus, Genus Morbili virus, Family
Paramyxoviridae
The disease was first discovered in 1950
in South Africa, in 1983 in the USA.
Size
of virus:
Variable size, 150-250nm. Single
negative-strand RNA virus.
Negative sense RNA: Whose sequence
is complementary to mRNA. Therefore it is first converted to Positive sense RNA
before transcription.
More than 20 strains and each strain
has different pathogenicity. The virus can survive at low temperatures 0-4C
(survives for 7 days at this temperature). At 50-60C, it is capable to survive
up to 30 minutes. Humidity and low temperature increase its survival. At -65C
it can survive up to 7 years. At 37C it can survive up to 3 days.
pH
4.5-9 is more viable. Less than or
more than this pH will result in less survival of the virus.
0.3% carbolic acid can be used to destroy
it.
Host
range:
Ø Canidae
Ø Felidae
Ø Pandas
Ø Ferrets
Ø ……..
Epidemiology:
Present throughout the world.
Prevalence is more in Asia, controlled in the USA.
Transmission:
From infected animals to healthy
animals is through aerosol, secretions, shedding (7 days), shedding in urine
also. The virus could be secreted up to 60-70 days post-infection. Also transplacental transmission.
Built-in CD virus in Newborn
puppies. Signs appear in them at the age of 4-6
weeks. From the dam to puppies. Animal remains carrier throughout its life
and this is the major reason that disease cannot be controlled.
Contact of diseased or carrier
animal. Recovered animal gets lifelong immunity.
Vaccination:
Through vaccination, immunity is not lifelong. The immunized animal will develop signs and symptoms when the contact with diseased
or carrier animal occurs.
25-75% of the canine
population is infected from CD virus and
become carriers throughout life. (Virus
resides in CNS)
Age:
In cosmopolitan dogs 3-6 months
Isolated dogs: can be affected at
any age. Severity is much greater than cosmopolitan.
Brachiocephalic
animals (Flat and wide skull shape):
Severity and
prevalence are less.
Dolichocephalic
dogs (Having a narrow and long head):
More severity and
prevalence. Fewer chances of survival.
Mesaticephalic
dogs (A skull with
the cranium and nasal cavity about equal lengths)
Strains:
1) Synder hill ( causes polioencephalomalacia )
2) A 75/17
3) R2 S2
These all strains are highly
virulent. Fewer chances of survival.
Pathogenesis:
Systemic
infection
It gains entry through aerosol. So 1st
it resides in the epithelium of URT. Up to 24 hours, it multiplies there. Then it
is transferred to tonsils, bronchial and retropharyngeal lymph nodes.
Multiplies in these organs up to 2-4 days post-infection. Viremia develops
which is transferred to the spleen, lamina propria of the stomach and small intestine,
mesenteric lymph nodes, kupffer cells of the liver. Multiplication in these organs occurs
after 4 days post-infection.
After 6 days post-infection, fiver,
leukopenia (primarily lymphopenia). Then shedding of the virus starts.
9-14 days post infection:
1)
Strong immune system
If the strong immune system, it will
clear the virus from the body of an animal. This animal will not be the carrier of
virus.
2)
Intermediate immune system
The virus multiplies in the spleen, stomach,
small intestine, liver and spreads to CNS and the integumentary system. After the
virus has reached to CNS, the animal will become carriers of the virus. The animal may or
may not show the signs of disease but it is a carrier of the CD virus.
3)
Weak immune system
Severe signs of disease. More
chances of death. The virus spreads to all body systems.
CNS
infections
After entry in CNS, Virus maybe
free or lymphocyte-associated, 3 target sites in CNS:
i)
Perivascular
of meninges
ii)
Choroid
plexus of 4th ventricle
iii)
Ependymal
structures ( cells of ventricles )
The most productive of these is the choroid
plexus i.e. it spreads the virus further to
i)
Spinal
cord
ii)
Cerebral
structures
iii)
Subpial
iv)
CSF
Factors which prevent
further spread of the virus:
i)
Age
of animal
ii)
Immune
status
iii)
How
much neurotropic is the strain of virus
Clinical
signs
There is variation in clinical signs
Ø Systemic signs
Ø Neurologic signs
Ø Neonatal signs
Ø Bone lesions
Ø Ocular signs
Systemic
signs
Depend upon
Ø Virulence of strain
Ø Environmental condition
Ø Age of the animal
Ø Immune system
Signs
are:
i)
Fiver
(104-106F)
ii)
Dullness
iii)
Anorexia
iv)
Depression
v)
Mucopurulent
discharge from nostril
vi)
Dry
cough and then convert to productive cough
vii)
Keratoconjuctivitis
viii)
Persistent
anosmia
ix)
More
lower respiratory sounds ( through auscultation )
x)
Vomiting
un related to eating
xi)
Diarrhea
(shooting). Could be blood-tinged. Could have mucus in it.
xii)
Dehydration
xiii)
Academia
xiv)
Tenesmus
xv)
Sudden
death
Neurological
signs
These signs can occur simultaneously
with systemic infection but this case is rare. Mostly neurological signs occur
1-3 weeks after recovering from systemic infection.
Nervous signs are always progressive
These signs define mortality
These signs include:
i)
Hyperesthesia
ii)
Par
paresis
iii)
Tetra
paresis
iv)
Chewing
gum reflexes
v)
Seizures
vi)
Champing
of jaws
vii)
Chorea
viii)
Myoclonus
(involuntary twitching of muscles) or involuntary movement of any body part.
ix)
Paralysis
of forelimbs associated with myoclonus
x)
Ataxia
xi)
Cervical
stiffness
These signs are more rhythmic while the animal is sleeping.
Trans
placental infections:
If the dam survives from CD, following
signs may occur
Ø Stillbirth ( dystocia )
Ø Abortion
If puppies are born alive, signs of
CD will appear at the age of 4-6 weeks. Mostly neurological signs appear in
them.
Neonatal
infections: (Neonate: fetus of 1st
28 days)
Signs in neonates include:
i)
Week
dentin
ii)
Enamel
hypoplasia
iii)
Bone
lesions
iv)
Metaphyseal
osteosclerosis of long bones ( hardening of bone in the metaphyseal region )
v)
Keratoconjunctivitis
which may lead to blindness
Treatment
No specific treatment. Supportive
treatment is done to increase the chances of survival.
Prevention
and control
Ø Vaccination is the foremost preventive measure
Ø 3-4 weeks of age------------ 1st shot of CD
Ø Again another shot after 3-4 weeks
Ø Also 3rd time
Ø If the disease is prevalent in the area, then the duration between
shots should be less (2-3 weeks)
Ø Isolate the infected animal and clean the Kennel with any
disinfectant
Ø No zoonotic risk
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